In hospital environments, the transport of patients on a hospital bed or of the hospital beds themselves is required. For this reason, beds are fitted with a system of casters allowing handling. But the handling of heavy beds, or beds with a patient, can be physically uncomfortable. For this reason, hospital beds are equipped with additional systems for propelling a bed, for example, in the form of a motorized wheel, making bed transport easier for hospital personnel. The aforementioned system constitutes a known state of art, for example, according to U.S. Pat. Nos. 5,806,111, 6,505,359 or 7,090,041.
The motorized wheel is connected to the undercarriage and can be forced against the ground for the purposes of motorised movement or retracted into the undercarriage for the purposes of handling the bed without engagement of motorised movement, as in patent application EP2298263.
One important element of the system for propelling a bed is its control equipment. In one common embodiment, such as, in the U.S. Pat. No. 6,330,926, the bed is equipped with push bars having a mechanical switch by which the user activates the motorized movement of the bed. Another of the alternatives, according to U.S. Pat. No. 6,752,224, is the control of a drive system via push bars equipped with force sensors located between the push bars and the bed. These sensors convert the force, which arises, for example, through the movement of the push bars in the required direction of travel, to a signal controlling the bed's movements. The push bars in the aforementioned patent can be equipped with a user presence detector, which is implemented, for example, using a force sensor. Alternatively, an air or liquid pressure sensor or capacity sensor can be used for this purpose.
In the known state of art, the system for propelling a bed is activated by a main switch located on the undercarriage near the battery (U.S. Pat. No. 6,330,926), and which connects the motor and the battery. Without switching on the main switch, it is possible to manipulate the bed manually, without the use of an additional system for powering the bed, in this specific example, thanks to a clutch.
Another known solution for propelling a bed is implemented in the form of a motorized wheel capable of rotating around a vertical axis, which enables the user to move the bed in all directions. This solution is contained, for example, in patent application WO2009113009.
Motorized movement of a bed entails danger, in cases where the personnel stops controlling the bed as a result of an accident or inattention. For these cases, safety elements are included in the bed control, intended to brake the bed. In this way, the bed is essentially braked for safety reasons in cases where the control of the bed by the personnel is interrupted. So, in U.S. Pat. No. 7,007,765, the bed is braked by the friction of unpowered drive for propelling, if the pressing of the mechanical switch is interrupted. One common means of braking a bed is by shorting out the motor. Such a solution is described in patent CA2469462, for example. One problem of beds allowing motorized movement, compared with conventional non-propelled beds, is their more difficult manipulation in a tight space, because the beds are often only capable of motorized movement in one or more directions, and braking. Another shortcoming of beds with a motorized system is the necessity of drawing power from batteries even during a very small movement of the bed. For systems in the known state of art, it is not possible for the operator to make fine movements to a bed using their own power, if the main or another separate switch is not used, for disconnection of the shorting circuit of the motor, or for activation of the clutch. For this reason, it is very difficult for the user to switch from motorized movement to manual mode, enabling the wheel to rotate freely.
The aim of this invention is to propose a solution for controlling the drive system of a hospital bed, ensuring for the hospital personnel safe and practical handling of the bed in the motorized movement, manual movement and bed braking modes.